The present invention relates to thermoplastic compositions of polyurethanes and alkyl acrylate copolymers.
The compositions according to the invention are suitable for the production of films, seals, coatings, injection-molded and extruded articles. The compositions may also be processed by calendering or thermoforming, so that it is possible, for example, to produce laminated plastic films of comfortable appearance and feel. Films such as these are of considerable significance for the interior trim of motor vehicles, in the decorative field, in the furniture industry, in the building industry or as artificial leather. Typically, materials of the type in question often contained polyvinyl chloride ("PVC") in admixture with other polymers or plasticizers and, thus, generally contained halogen. In addition, they often contained volatile components with a tendency to migrate (such as, e.g., plasticizers, stabilizers, and processing aids). For ecological reasons (such as reusability, waste disposal, reduction of pollutant emission in the event of fire) there has recently been a demand for halogen-free substitutes. In addition, the migratable components of the known materials lead to unsatisfactory ageing behavior under the effect of heat. For these reasons, there is a demand for new plastics capable of replacing PVC-containing molding compounds.
Various polymer blends with polyurethanes are already known. British Patent 2,021,600 describes blends of thermoplastic polyurethanes and ABS. The disadvantage of these blends lies in their poor resistance to ageing and hydrolysis. These molding compositions are not suitable for the production of soft, flexible films.
European Patent 12,416 (believed to correspond to U.S. Pat. No. 4,317,890) describes thermoplastic compositions of polyurethanes and rubber graft copolymers. Typical of the rubber copolymers described are acrylate rubber and graft monomers, such as styrene, o-methyl styrene and acrylonitrile. The disadvantage of these graft copolymers is that they adversely affect surface quality when used in relatively large quantities, so that it is not possible to produce soft, flexible films.
Thermoplastic blends of thermoplastic polyurethane, fibrous reinforcing materials and a polar polymer are known from European patent 12,417 (believed to correspond to U.S. Pat. No. 4,500,671). The polar polymer contains polar and apolar monomer units, such as alkyl acrylates, alkyl methacrylates, acrylonitrile, styrene and o-methyl styrene, and butadiene/isoprene and/or acrylate units. The polar polymer may be present as a homopolymer, copolymer or graft copolymer. Crosslinked polar polymers are not preferred. The disadvantage of such compositions is that the polar polymers lead to molded products which are affected by ageing and hydrolysis and which, in addition, have surfaces of poor quality and an unpleasant, rubber-like feel where the polar polymers are used in relatively large quantities.
The problem addressed by the present invention was to provide thermoplastic compositions having improved surfaces, improved processibility by calendering and thermoforming and an attractive range of properties for leather substitutes, including an aesthetic feel and grain stability.